They performed experiments using rats, and say they confirmed for the first time that low to moderate levels of alcohol alter beta-endorphin release in a region of the brain linked to drug and alcohol addiction, producing "the pleasant effects that likely reinforce alcohol consumption."
Gianoulakis tells WebMD that researchers don't know the mechanisms responsible for the fact "that some people can stop after one-two drinks while others cannot."
"One way that alcohol may influence brain function is by increasing or decreasing the release of a number of neurotransmitters, among which are the endogenous opioid peptides, in distinct brain regions important for drug addiction," she tells WebMD.
So small to moderate alcohol consumption has positive effects on mood or attitude, and the source of these positive benefits can be traced. It's another good reason for enjoying a glass or two of wine in the evening, though not necessarily a good reason to start drinking alcohol if you don't already drink. It's still not clear if the positive health benefits of alcohol outweigh the negative effects in the long term — and that comparison simply may not be possible, since it's so hard to quantify something like improved mood.